Hi,
I have a W208 and i live in Europe, i really think that MB for US have special soft pakage...
I can tell you this because my CLK 430 is quite stiff also with original SHOK absorber.
I think you just have to change yours with adjustable KONI (2 types : red for SPORt with 3 position and Yellow for RACE with also 3 position).
I put on mine the Yellow one and in the postion 0 the car i really stiff i think it is bettre put the RED one.
If you are not happy you can also cahge springs with H&R or EIBACH but you have to decide.
I am back from a trip in Germany were i ride for many mile between 120 and 150 mph and i can tell you that siffer is better .
Hope this help you
Alberto